1) Can they use Nanobots?

2) Can they use Taunt as one part of the multi-attack, while still having the second Multi-attack available?

As long as the meet the prerequisites (2 damage or less). They can't heal past their starting click, though (so no making a 100 point Sentinel go up into the 200 point dial).

Yes, it is a power action against a target, which is what is required of a multi-attack (the 'against a target' part, that is. it doesn't necessarily have to be a power action...).

####! This is what I get for listening to my opponent at a venue.